Photoconductive device and method of operating the same

Abstract

A photoconductive device having a photoconductive layer which includes an amorphous semiconductor layer capable of charge multiplication in at least a part thereof is disclosed. The method of operating such a photoconductive device is also disclosed. By using the avalanche effect of the amorphous semiconductor layer, it is possible to realize a highly sensitive photoconductive device while maintaining low lag property.

What is claimed is: 
     
       1. An imaging device having high sensitivity and low dark current comprising: a semiconductor region having an amorphous semiconductor layer into which photons are inserted and converted into electron-hole pairs by photoelectric conversion;   means for applying a high electric field to the semiconductor region comprising an electrode and an electric power supply; and   means for reducing dark current of the imaging device,   wherein the amorphous semiconductor layer generates electron-hole pairs under said high electric field such that a number of said electron-hole pairs is larger than the number of incident photons.   
     
     
       2. The device as set forth in claim 1 wherein the means for reducing dark current is a layer disposed between the semiconductor region and the electrode. 
     
     
       3. An imaging device comprising: a photoconductive region for converting incident photons into charge carriers therein and having a charge multiplication region;   means for applying an electric field into the photoconductive region so as to make the carriers run in the photoconductive region in accordance with a direction of the electric field;   wherein the imaging device operates so that the charge multiplication occurs in a charge multiplication region when the electric field is applied to the photoconductive region by the means for applying an electric field.   
     
     
       4. The device as set forth in claim 3 wherein the device further comprises means for reducing dark current.